It's a well-known diet rule that if you want to stay slim, the secret is to eat a low-calorie diet and exercise regularly.
However, if you snack on and drink low-calorie substitutes, you're more likely to gain the pounds than shift the flab.
Researchers from the Purdue University in Indiana discovered that the taste of fat and sugar causes the body to expect a calorific buzz. But when it doesn't get its desired high-calorie hit, the body gets confused and makes us eat more.
The study came to this conclusion by feeding two groups of lab rats crushed crisps. One group was given a mixture of high-fat and fat-substitute crisps, while the other group was fed only full-fat crisps.
After 28 days, researchers found the animals that ate a diet supplement of fat-substitute crisps gained more weight and fatty tissue than those on full-fat crisps.
"Substituting a part of the diet with a similar tasting item that has fewer or zero calories sounds like a common-sense approach to lose weight, but there are other physiological functions at work," says Professor Susan Swithers from the study.
"These substitutes are meant to mimic the taste of fat in foods that are normally high in fat while providing a lower number of calories, but they may end up confusing the body. Tastes normally alert the body to expect calories, and when those calories aren't present we believe the systems become ineffective and one of the body's mechanisms to control food intake can become ineffective."
"We are looking at an animal model, but there are similarities for humans, and based on what we found, we believe that our findings question the effectiveness of using fat substitutes as part of a long-term weight loss strategy," added co-author of the study, Professor Terry Davidson.
If you're cutting down on your calorie intake but want to do it sensibly, take a look at these healthy low-calorie snacks that don't substitute fat or sugar.
Calorie-count: 55 calories per cupful of plain home-made popcorn with one teaspoon of oil If you don't have a microwave handy to pop your own, most fast food chains now stock low-calorie packs in a variety of flavours, including salt or sugar and salt. The modern pre-packed varieties will bump up your calorie count to approximately 125 calories. But steer clear of the old-school sticky toffee varieties as these are laden with sugar and calories.
Calorie count: 130 calories for 2 slices There are times when only cake will do - like 4pm when the sugar slump strikes. Satisfy your sweet cravings with the next best thing - cinnamon raisin toast. Top with low-fat spread or a drizzle of honey.
Calorie count: 100 calories per 85g tin of tuna (in water) Spread a small can of tuna on a rye crispbread for a mid-morning snack that will keep you full until lunchtime. Tuna is a great source of low-fat protein and is packed with Omega-3 fatty acid, renowned for its brain-boosting and mood-enhancing properties.
Calorie count: 104 calories for one cup If your idea of the perfect afternoon snack is a bag of Haribo, try sucking on frozen grapes instead. Rich in vitamins A, C, B6 and folate as well as the powerful antioxidants, flavanoids, grapes have been widely used to treat constipation, indigestion, fatigue, kidney disorders, asthma, heart disease and migraines.
Calorie count: 165 calories per ounce Sunflower seeds are a low-fat alternative to crisps when you need that crunchy, savoury hit. They are packed with vitamins such as vitamin B1 and B5, vitamin E and folate and also provide a healthy dose of minerals including copper, magnesium, selenium and phosphorous-important minerals.
Calorie count: 183 calories per one ounce Scientists claim eating just seven walnuts a day could help ward off disease and fight cholesterol. The antioxidants found in raw walnuts were found to be 15 times as powerful as Vitamin E, which can protect the body against damaging natural chemicals.
Calorie-count: 47 calories per handful Olives are rich in Vitamin E, which helps maintain healthy skin and gut. They are also a good source of antioxidants, essential for a strong immune system.